Deterioration of timber and other substrates in the environment is a constant concern of the lumber and wood products industry and in agriculture. Infestation by brown rot fungi, for example, which attack at least the cellulose and hemicellulose of hardwoods or softwoods, is a major cause of decay, and has proved costly and difficult to control. Timber which is storaged or permanently exposed to the environment, such as construction materials, utility poles or railroad ties, must typically be impregnated or otherwise treated with fungicidal agents to obtain a useful life therefrom. Live substrates such as tree wounds if left unprotected also are vulnerable to invasive fungal decay, resulting in economic loss, particularly to the agricultural industry.
For preventing wood decay caused by fungal and other microbial agents, workers in the art have come to rely on the biocidal action of certain compounds of recognized toxicity in the environment, such as chlorinated hydrocarbons, inorganic and organic metal salts (e.g., arsenates, chromates, borates), and alkylaluminum compounds, representative ones of which comprise pentachlorophenol, copper chromium arsenate, acid copper chromate, chromated zinc chloride, copper naphthenate, and dodecyldimethylammonium chloride, see Nicholas et al., "Interaction of Preservatives with Wood," in The Chemistry of Solid Wood, ACS, 1984. Many of such compounds, moreover, are commonly formulated with petroleum-based and other organic solvent vehicles, which solvents in themselves are often considered environmental contaminants, and may be costly and hazardous to handle, besides being restricted from certain agricultural applications. The well-known creosote oils are also commonly derived from oil or coal tar fractions. Alternatively, the water-soluble compounds, such as inorganic metal salts, if not readily fixed within the substrate, tend to be leached by moisture to form toxic or corrosive residues in the environment. As a result, the selection of anti-microbial agents for preservation purposes is becoming increasingly circumscribed by environmental regulations.
It has been an object to identify more environmentally compatible materials and compositions which can be applied to a substrate to inhibit or control environmentally-induced deterioration or decay, and in particular, decay caused by microorganisms such as fungi.
It has been a further object to provide preservative compositions which can be employed in agricultural uses.